Slurry composition for lithium ion electrical storage devices

ABSTRACT

The present invention is directed to a lithium ion battery electrode slurry composition comprising: (a) an electrochemically active material capable of lithium intercalation and deintercalation; (b) a binder dispersed in an aqueous or organic medium and comprising a reaction product of a reaction mixture comprising one or more epoxy functional polymer(s) and one or more acid functional acrylic polymer(s); and (c) an electrically conductive agent. The present invention also provides an electrode comprising: (a) an electrical current collector; and (b) a cured film formed on the electrical current collector. The cured film is deposited from the slurry composition described above. Electrical storage devices prepared from the electrode are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/638,448, filed on Jun. 30, 2017, which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to electrode slurry compositions thatcontain a binder, which in turn comprises a reaction product of areaction mixture comprising one or more epoxy functional polymer(s) andone or more acid functional acrylic polymer(s). The slurry compositionsare useful in the manufacturing of electrodes for use in electricalstorage devices such as batteries. The present invention also relates toelectrodes comprising a cured film prepared from the slurrycompositions, and to electrical storage devices.

BACKGROUND OF THE INVENTION

Electrodes for electrochemical cells are usually manufactured byattaching an electrochemically active electrode material such as alithium compound to a current collector. Conventional current collectorsmay be rigid supports or flexible foils made from an electricallyconductive material such as copper or aluminum. The electrochemicallyactive electrode material may be prepared as a slurry or paste andsubsequently coated onto the current collector. Alternatively, theslurry is manufactured as a self-supporting layer which is laterattached to the current collector. Methods of attaching theelectrochemically active electrode material to the current collector mayinclude lamination, gluing with adhesives, or coating.

The slurry or paste usually comprises a mixture of an electrochemicallyactive material and a binder material. Further components such asconductive additives (i.e., carbon black, graphite, graphene, carbonfibers, VGCF (vapor grown carbon fibers, etc.) are also often includedin the slurry.

Polyvinylidene fluoride (PVDF) or polyvinylidenefluoride-hexafluoropropylene (PVDF-HFP) copolymers have demonstratedexcellent chemical and mechanical properties when used as a bindermaterial in a slurry for positive and negative electrodes. Inparticular, PVDF provides a good electrochemical stability and highadhesion to the electrode materials and to current collectors, making ita preferred binder material for electrode slurries. Typically, thepolyvinylidene is dissolved in an organic solvent and then the electrodematerial, such as an electrochemically active lithium compound and acarbonaceous material, is combined with the PVDF solution to form aslurry that is applied to a metal foil or mesh to form the electrode.

The role of the organic solvent is to dissolve PVDF in order to providegood adhesion between the electrode material particles and the metalfoil or mesh upon evaporation of the organic solvent. Unfortunately,there is only a small number of solvents in which PVDF is soluble.Currently, the organic solvent of choice is N-methyl-2-pyrrolidone(NMP). PVDF binders dissolved in NMP provide superior adhesion and aninterconnectivity of all the active ingredients in the electrode slurrycomposition. The bound ingredients are able to tolerate large volumeexpansion and contraction during charge and discharge cycles withoutlosing interconnectivity within the electrodes. Interconnectivity of theactive ingredients in an electrode is extremely important in batteryperformance, especially during charging and discharging cycles, aselectrons must move across the electrode, and lithium ion mobilityrequires interconnectivity within the electrode between particles.

However, NMP is a toxic material and presents health and environmentalissues. NMP is on the list of Chemicals Known to the State to CauseCancer or Reproductive Toxicity cited in California Proposition 65(1986). In the face of increasing regulation, some manufacturers areconsidering alternative solvents for some applications, especially whereworker exposure is difficult to control. It would therefore be desirableto develop electrode slurries that use binders other than PVDF,eliminating the need for NMP, and that provide acceptable performance,adhesive and chemical resistance properties.

The present invention thus aims to provide electrode slurry compositionsuseful for the manufacture of electrodes for use in electrical storagedevices such as batteries, which overcome or alleviate at least some ofthe afore-mentioned deficiencies of currently available conventionalelectrode slurry compositions. The present invention therefore is inparticular directed towards providing environmentally friendly electrodeslurry composition without adverse health effects, which exhibitcomparable or even better electrochemical performance, adhesive andchemical resistance properties compared to conventional electrode slurrycompositions that use a polyvinylidene fluoride polymer as binder.

SUMMARY OF THE INVENTION

The present invention provides a lithium ion battery electrode slurrycomposition comprising:

(a) an electrochemically active material capable of lithiumintercalation and deintercalation;

(b) a binder dispersed in an aqueous or organic medium and comprising areaction product of a reaction mixture comprising one or more epoxyfunctional polymer(s) and one or more acid functional acrylicpolymer(s); and

(c) an electrically conductive agent.

The present invention also provides an electrode comprising:

(a) an electrical current collector; and

(b) a cured film formed on the electrical current collector, wherein thecured film is deposited from the slurry composition described above andin more detail below.

The present invention furthermore relates to an electrical storagedevice, such as a battery, comprising:

(a) an electrode as described above and in more detail below,

(b) a counter electrode, and

(c) an electrolyte.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure provides a slurry composition useful in themanufacture of an electrode for an electrochemical cell. In particular,the present invention is directed to a slurry composition comprising:(a) an electrochemically active material capable of lithiumintercalation and deintercalation; (b) a binder dispersed in an aqueousor organic medium and comprising a reaction product of a reactionmixture comprising one or more epoxy functional polymer(s) and one ormore acid functional acrylic polymer(s); and (c) an electricallyconductive agent. The electrode slurry can be used to prepare anelectrode for a lithium ion electrical storage device such as a battery.

The electrochemically active material (a) in the electrode slurry can beselected according to the type of electrical storage device of interest.For example, for the preparation of positive electrodes, theelectrically active material (a) typically comprises electrochemicallyactive lithium compounds capable of lithium intercalation anddeintercalation. Examples include lithium-containing oxides andphosphates such as LiCoO₂, LiNiO₂, LiFePO₄, LiCoPO₄, LiMnO₂, LiMn₂O₄,Li(NiMnCo)O₂, Li(NiCoAl)O₂, carbon-coated LiFePO₄ or mixtures orcombinations of any of the foregoing. For the preparation of negativeelectrodes, the electrically active material (a) may comprise graphite,silicon, including silicon compounds such as silicon oxides, tin,including tin compounds and alloys, or a mixture or combination of anyof the foregoing. The electrochemically active material (a) can bepresent in the slurry in amounts of at least 45 percent by weight, suchas at least 50 percent by weight, or at least 70 percent by weight,based on the total weight of solids in the slurry. The electrochemicallyactive material (a) can for example be present in the slurry in inamounts of up to 98 percent by weight, such as up to 95 percent byweight, or up to 80 percent by weight, based on the total weight ofsolids in the slurry.

The binder (b) may be dispersed in an aqueous or organic medium andcomprises a reaction product of a reaction mixture comprising one ormore epoxy functional polymer(s) and one or more acid functional acrylicpolymer(s). As used herein, an “aqueous medium” refers to a liquidmedium comprising at least 50 weight % water, based on the total weightof the liquid medium. Such aqueous liquid mediums can for examplecomprise at least 60 weight % water, or at least 70 weight % water, orat least 80 weight % water, or at least 90 weight % water, or at least95% water, based on the total weight of the liquid medium. The aqueousmedium may optionally further comprise one or more organic solvents.Non-limiting examples of suitable organic solvents for use in theaqueous medium or as an organic medium include polar organic solventse.g. protic organic solvents such as glycols, glycol ether alcohols,alcohols, and volatile ketones, glycol diethers, esters, and diesters.Other non-limiting examples of organic solvents include aromatic andaliphatic hydrocarbons.

The binder (b) and the slurry are usually essentially free of N-Methylpyrrolidone. By “essentially free” is meant that if a compound ispresent in a composition, it is present incidentally in an amount ofless than 0.1 percent by weight, often less than 0.05 percent by weightor less than 0.01 percent by weight, usually less than trace amounts.The compound is therefore generally not present in an amount sufficientto affect any properties of the composition.

The binder (b) can in principle comprise any reaction product of areaction mixture comprising one or more epoxy functional polymer(s) andone or more acid functional acrylic polymer(s). The reaction product maycomprise one or more polymers having epoxy, hydroxyl, and/or acidfunctionality. Note that the phrase “and/or” when used in a list ismeant to encompass alternative embodiments including each individualcomponent in the list as well as any combination of components. Forexample, the list “A, B, and/or C” is meant to encompass seven separateembodiments that include A, or B, or C, or A+B, or A+C, or B+C, orA+B+C. The term “acrylic polymer” as used herein relates to additionpolymers derived from one or more acrylic monomer(s), i.e., acrylicacid, methacrylic acid (referred to together also as (meth)acrylic acid)and/or alkyl esters of (meth)acrylic acid, optionally with one or moreother polymerizable ethylenically unsaturated monomer(s). Useful alkylesters of acrylic acid or methacrylic acid include aliphatic alkylesters containing from 1 to 30, and often 4 to 18 carbon atoms in thealkyl group. Non-limiting examples include methyl methacrylate, ethylmethacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate, and2-ethyl hexyl acrylate. Suitable other copolymerizable ethylenicallyunsaturated monomers include for example vinyl aromatic compounds suchas styrene and vinyl toluene; nitriles such as acrylonitrile andmethacrylonitrile; vinyl and vinylidene halides such as vinyl chlorideand vinylidene fluoride and vinyl esters such as vinyl acetate.

The binder (b) is often prepared by chain extending one or morenon-epoxy functional acrylic polymer(s), prepared using any knownmethod, with one or more epoxy-functional chain extending agent(s). Inparticular, the binder can be prepared by chain extending one or moreacid-functional acrylic polymer(s) with one or more epoxy-functionalmaterial(s) that contain functional groups, which are reactive with theacid functionality of the acrylic polymer. The binder is often preparedfrom a mixture of polymers comprising one or more epoxy functionalpolymer(s) and one or more acid functional acrylic polymer(s).

Suitable epoxy functional polymers (which can be used together with oneor more acid functional acrylic polymers for preparing the binder (b))may be prepared by reacting together a polyepoxide and (i) a polyaminegroup-containing material and/or (ii) a polyhydroxyl group-containingmaterial selected from alcoholic hydroxyl group-containing materials andphenolic hydroxyl group-containing materials. The polyepoxide may alsobe reacted with a material containing both hydroxyl and amine groups.

The polyepoxide and a polyhydroxyl group-containing material may bereacted together neat or in the presence of an inert organic solventsuch as a ketone, including methyl isobutyl ketone and methyl amylketone, aromatics such as toluene and xylene, and glycol ethers such asthe ethyl ether of diethylene glycol. The reaction is usually conductedat a temperature of about 80° C. to 160° C. for about 30 to 180 minutesuntil an epoxy group-containing resinous reaction product is obtained.

The polyepoxide by definition has at least two 1,2-epoxy groups. Ingeneral, the calculated epoxide equivalent weight of the polyepoxidewill range from 100 to about 2000, typically from about 180 to 500. Theepoxy compounds may be saturated or unsaturated, cyclic or acyclic,aliphatic, alicyclic, aromatic or heterocyclic.

Examples of polyepoxides are those having a 1,2-epoxy functionalitygreater than one and usually about two; that is, polyepoxides which haveon average two epoxide groups per molecule. The most commonly usedpolyepoxides are polyglycidyl ethers of cyclic polyols, for example,polyglycidyl ethers of polyhydric phenols such as Bisphenol A,resorcinol, hydroquinone, benzenedimethanol, phloroglucinol, andcatechol; or polyglycidyl ethers of polyhydric alcohols such asalicyclic polyols, particularly cycloaliphatic polyols such as1,2-cyclohexane diol, 1,4-cyclohexane diol,2,2-bis(4-hydroxycyclohexyl)propane, 1,1-bis(4-hydroxycyclohexyl)ethane,2-methyl-1,1-bis(4-hydroxycyclohexyl)propane,2,2-bis(4-hydroxy-3-tertiarybutylcyclohexyl)propane,1,3-bis(hydroxymethyl)cyclohexane and 1,2-bis(hydroxymethyl)cyclohexane.Examples of aliphatic polyols include, inter alia, trimethylpentanedioland neopentyl glycol. A particularly suitable polyepoxide used toprepare the epoxy functional polymer is EPON 828, available fromMomentive Performance Materials Inc.

Polyhydroxyl group-containing materials used to react with thepolyepoxide to form the epoxy functional polymer may be any of thecyclic polyols, cycloaliphatc polyols, or aliphatic polyols listedabove. Polyhydroxyl group-containing materials used to react with thepolyepoxide may additionally be polymeric polyols. The equivalent ratioof reactants; i.e., the ratio of epoxy:hydroxyl groups, is typicallyfrom about 1.00:0.10 to 1.00:0.80.

Polyamine group-containing materials used to react with the polyepoxideto form the epoxy functional polymer may be primary or secondarydiamines or polyamines in which the radicals attached to the nitrogenatoms can be saturated or unsaturated, aliphatic, alicyclic, aromatic,aromatic-substituted-aliphatic, aliphatic-substituted-aromatic, andheterocyclic. Nonlimiting examples of suitable aliphatic and alicyclicdiamines include 1,2-ethylene diamine, 1,2-propylene diamine, 1,8-octanediamine, isophorone diamine, propane-2,2-cyclohexyl amine, and the like.Nonlimiting examples of suitable aromatic diamines include phenylenediamines and toluene diamines, for example o-phenylene diamine andp-tolylene diamine. Polynuclear aromatic diamines such as 4,4′-biphenyldiamine, methylene dianiline and monochloromethylene dianiline are alsosuitable.

Examples of suitable aliphatic diamines include, without limitation,ethylene diamine, 1,2-diaminopropane, 1,4-diaminobutane,1,3-diaminopentane, 1,6-diaminohexane, 2-methyl-1,5-pentane diamine,2,5-diamino-2,5-dimethylhexane, 2,2,4- and/or2,4,4-trimethyl-1,6-diamino-hexane, 1,11-diaminoundecane,1,12-diaminododecane, 1,3- and/or 1,4-cyclohexane diamine,1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, 2,4- and/or2,6-hexahydrotolylene diamine, 2,4′- and/or4,4′-diamino-dicyclohexylmethane and3,3′-dialkyl-4,4′-diamino-dicyclohexyl methanes (such as3,3′-dimethyl-4,4′-diamino-dicyclohexyl methane and3,3′-diethyl-4,4′-diamino-dicyclohexyl methane), 2,4- and/or2,6-diaminotoluene and 2,4′- and/or 4,4′-diaminodiphenyl methane, ormixtures thereof. Cycloaliphatic diamines are available commerciallyfrom Huntsman Corporation (Houston, Tex.) under the designation ofJEFFLINK™ such as JEFFLINK™ 754. Additional aliphatic cyclic polyaminesmay also be used, such as DESMOPHEN NH 1520 available from BayerMaterial Science and/or CLEARLINK 1000, which is a secondary aliphaticdiamine available from Dorf Ketal. POLYCLEAR 136 (available fromBASF/Hansen Group LLC), the reaction product of isophorone diamine andacrylonitrile, is also suitable. Other exemplary suitable polyamines aredescribed in U.S. Pat. No. 4,046,729 at column 6, line 61 to column 7,line 26, and in U.S. Pat. No. 3,799,854 at column 3, lines 13 to 50, thecited portions of which are incorporated by reference herein. Additionalpolyamines may also be used, such as ANCAMINE polyamines, available fromAir Products and Chemicals, Inc.

Suitable materials containing both hydroxyl and amine groups includehydroxyalkylamines such as hydroxyethylamine and the like.

The epoxy functional polymer usually has an epoxy equivalent weight ofat least 3500 or at least 5500. Typically the epoxy functional polymerhas an epoxy equivalent weight of up to 11000. The epoxy equivalentweight may for example be in a range from 3500-11000, or 5500-6500, or9000-11000. The epoxy equivalent weight can be measured using titrationwith 0.1 N perchloric acid according to ASTM D1652 (published in ASTMVolume 06.03).

Suitable acid functional acrylic polymers useful to react with the epoxyfunctional polymer(s) as described above to prepare the binder (b) ofthe slurry compositions according to the present invention includecopolymers of one or more alkyl esters of acrylic acid or methacrylicacid, together with at least one acid functional ethylenicallyunsaturated monomer and optionally one or more other polymerizableethylenically unsaturated monomers. Useful alkyl esters of acrylic acidor methacrylic acid include aliphatic alkyl esters containing from 1 to30, and usually 4 to 18 carbon atoms in the alkyl group. Non-limitingexamples include methyl methacrylate, ethyl methacrylate, butylmethacrylate, ethyl acrylate, butyl acrylate, and 2-ethyl hexylacrylate. Suitable other copolymerizable ethylenically unsaturatedmonomers include vinyl aromatic compounds such as styrene and vinyltoluene; nitriles such as acrylonitrile and methacrylonitrile; vinyl andvinylidene halides such as vinyl chloride and vinylidene fluoride andvinyl esters such as vinyl acetate.

The acid functional acrylic polymer includes acid functional groups,which are often incorporated into the polymer by including one or moreacid functional monomers in the reactants used to produce the copolymer.Useful ethylenically unsaturated acid functional monomers used toprepare the acid functional acrylic polymer include for examplemonocarboxylic acids such as acrylic acid, methacrylic acid, crotonicacid; dicarboxylic acids such as itaconic acid, maleic acid and fumaricacid; and monoesters of dicarboxylic acids such as monobutyl maleate andmonobutyl itaconate.

The acid functional acrylic polymer usually has a calculated(theoretical) acid value in the range of 20-150. It may also be measuredusing a titration method with 0.1 N KOH.

To prepare the binder (b), the epoxy functional polymer and acidfunctional acrylic polymer may be mixed together and heated to atemperature of 50 to 150° C. in order to chain extend or build themolecular weight of the polymer. The reaction product may comprise oneor more polymers having epoxy, hydroxyl, and/or acid functional groups,which may be influenced by the stoichiometry of the reactants. Acid andhydroxyl functional groups are useful in the preparation of aqueousdispersions. Excess acid functional groups may be neutralized with anamine such as dimethylethanolamine to facilitate dispersion in water.For dispersions in organic media, up to ten percent of the functionalgroups in the binder (b) may be epoxy functional. In certain examples ofthe present invention, the mixture of polymers used to prepare thebinder (b) of the slurry composition of the present invention comprisesat least 70 percent by weight of one or more epoxy functional polymer(s)and up to 30 percent by weight of one or more acid functional acrylicpolymer(s), wherein the percentages by weight are based on the totalweight of the reaction product in the binder (b).

The binder (b) may further comprise a crosslinking agent, such as anaminoplast, a polycarbodiimide, and/or a polyepoxide. Useful aminoplastscan for example be obtained from the condensation reaction offormaldehyde with an amine or amide. Nonlimiting examples of amines oramides include melamine, urea and benzoguanamine.

Although condensation products obtained from the reaction of alcoholsand formaldehyde with melamine, urea or benzoguanamine are most common,condensates with other amines or amides can be used. Formaldehyde is themost commonly used aldehyde, but other aldehydes such as acetaldehyde,crotonaldehyde, and benzaldehyde can also be used.

The aminoplast can contain imino and methylol groups. In certaininstances, at least a portion of the methylol groups can be etherifiedwith an alcohol to modify the cure response. Any monohydric alcohol likemethanol, ethanol, n-butyl alcohol, isobutanol, and hexanol can beemployed for this purpose. Nonlimiting examples of suitable aminoplastresins are commercially available from Cytec Industries, Inc. under thetrademark CYMEL® and from Solutia, Inc. under the trademark RESIMENE®.

Suitable carbodiimide crosslinkers include an aliphatic and/orcycloaliphatic dinitrogen analogue of carbonic acid of the generalizedstructure: RN═C═NR1 where Rand R1 are independently aliphatic orcycloaliphatic groups. The aliphatic groups can comprise 1-6 carbonatoms. Examples include dibutyl carbodiimide and dicyclohexylcarbodiimide. Oligomeric or polymeric carbodiimide crosslinkers can alsobe used. Examples of such materials are disclosed in United StatesPatent Application Publication Number 2009/0246393 A1.

Examples of polyepoxides suitable as crosslinking agents include lowmolecular weight polyepoxides such as 3,4-epoxycyclohexylmethyl3,4-epoxycyclohexanecarboxylate andbis(3,4-epoxy-6-methylcyclohexyl-methyl) adipate. Higher molecularweight polyepoxides, including the polyglycidyl ethers of polyhydricphenols and alcohols described above, are also suitable as crosslinkingagents.

The amount of the crosslinking agent in the binder (b) is generally atleast I percent by weight, such as at least 2 percent by weight, or atleast 3 percent by weight, based on the total weight of resin solids inthe binder (b). The amount of the crosslinking agent in the binder (b)is typically up to 5 percent by weight, such as up to 4 percent byweight, based on the total weight of resin solids in the binder (b). Thecrosslinking agent, if present, may for example be used in an amount inthe range from 1 to 5, or from 3 to 5, or from 2 to 4 percent by weight,based on the total weight of resin solids in the binder (b).

The binder (b) is typically essentially free of any polyvinylidenefluoride (PVDF) polymers.

The binder dispersed in the aqueous or organic medium may be used tobind the electrically active material (a) to a conductive substrate; e.g., an electrical current collector, such as a sheet or foil comprisingaluminum or copper, in an electrode.

The binder can be present in the electrode slurry composition of thepresent invention in amounts of at least 0.1 percent by weight, such asat least I percent by weight, based on the total weight of solids in theslurry. The binder can be present in the electrode slurry composition ofthe present invention in amounts of up to 30 percent by weight, or up to20 percent by weight, or up to 10 percent by weight, or up to 7 percentby weight, based on the total weight of solids in the slurry. The bindercan for example be present in the electrode slurry composition of thepresent invention in an amount of 1 to 20 percent by weight, or 1 to I0percent by weight, or 4 to 7 percent by weight, based on the totalweight of solids in the slurry.

The electrode slurry further comprises (c) an electrically conductiveagent. Examples of suitable conductive agents include carbonaceousmaterials, such as graphite, activated carbon, acetylene black, furnaceblack, carbon fibers, fullerene and mixtures or combinations of any ofthe afore-mentioned. A particular example is TIMCAL C-NERGY™ Super C65conductive carbon, available from TIMCAL Ltd. The electricallyconductive agent (c) is usually present in the slurry in amounts of atleast 1 percent by weight, or 5 percent by weight, based on the totalweight of solids in the slurry. The electrically conductive agent (c) isusually present in the slurry in amounts of up to 20 percent by weight,or up to 10 percent by weight, or up to 9 percent by weight, based onthe total weight of solids in the slurry. The electrically conductiveagent (c) can for example be present in the electrode slurry compositionof the present invention in an amount of 1 to 20 percent by weight, or 5to 10 percent by weight, or 5 to 9 percent by weight, based on the totalweight of solids in the slurry.

The electrode slurry often further contains a thickener to preventsettling of the solids while providing appropriate slurry viscosity forcoating a current collector. Examples of the thickener include celluloseand derivatives thereof such as carboxymethyl cellulose, methylcellulose and hydroxypropyl cellulose; ammonium salts and alkali metalsalts of the above cellulose derivatives; polycarboxylic acids such aspoly(meth)acrylic acid and modified poly(meth)acrylic acid; alkali metalsalts of the above polycarboxylic acids; polyvinyl alcohol-based(co)polymers such as polyvinyl alcohol, modified polyvinyl alcohol andethylene-vinyl alcohol copolymer; water-soluble polymers such assaponified products of a copolymer of an unsaturated carboxylic acidsuch as (meth)acrylic acid, maleic acid or fumaric acid and a vinylester and anionic (meth)acrylic polymer thickeners.

Commercially available products of these thickeners include CMC1120,CMC1150, CMC2200, CMC2280 and CMC2450 (of Daicel Chemical Industries,Ltd.) as alkali metal salts of carboxymethyl cellulose and ACRYSOL ASE60 and 75 anionic (meth)acrylic polymer thickeners from Dow Chemical Co.

The content of the thickener, if present in the electrode slurrycomposition, is usually at least 0.1 percent by weight, or 0.5 percentby weight, based on the total weight of solids in the electrode slurry.The thickener, if present, is usually used in an amount of up to 30percent by weight, or up to 25 percent by weight, or up to 15 percent byweight, or up to 10 percent by weight, based on the total weight ofsolids in the electrode slurry. The optional thickener can for examplebe present in the electrode slurry composition of the present inventionin an amount of 0.1 to 15 percent by weight, or 0.5 to 10 percent byweight, based on the total weight of solids in the electrode slurry.

In addition to water or solvent incorporated into the slurry as themedium of the binder (b), water and/or solvent may be added as aseparate component of the slurry. For example, water or organic solventmay be present in the electrode slurry in an amount of at least 20percent by weight, or at least 30 percent by weight, based on totalweight of the slurry. Additionally, water or organic solvent may bepresent in the electrode slurry of the present invention in an amount ofup to 80 percent by weight, or up to 70 percent by weight, or up to 60percent by weight. The electrode slurry composition of the presentinvention can for example contain from 20 to 80 percent by weight, orfrom 20 to 70 percent by weight, or from 30 to 60 percent by weight, ofwater or organic solvent, based on total weight of the slurry.

When the binder (b) is in an aqueous dispersion, the electrode slurrymay contain an organic solvent or diluent to improve the stability andcoatability of the slurry. Examples of the organic solvent includealcohols such as 2-butoxyethanol; ketones such as methyl ethyl ketone,cyclohexanone, isophorone, acetophenone; phosphates such as triethylphosphate, and ethers such as C1 to C4 alkyl and dialkyl ethers ofethylene and propylene glycol, or any of those listed above as asuitable medium of the binder (b). The solvent may be incorporated intothe slurry as a component of the binder (b), and/or as a separatecomponent of the slurry as noted above. When used with an aqueousdispersion, the organic solvent is typically present in amounts of atleast 2 percent by weight, such as at least 10 percent by weight, basedon total weight of the slurry. When used with an aqueous dispersion, theorganic solvent is typically present in amounts of in an amount of up to60 percent by weight, or up to 50 percent by weight, or up to 30 percentby weight, based on total weight of the slurry. For example, the organicsolvent may present in the electrode slurry composition of the presentinvention in an amount in the range from 2 to 50 percent by weight, orfrom 10 to 30 percent by weight, based on total weight of the slurry. Asnoted above, the slurry is usually essentially free of NMP.

The electrode slurry can be manufactured by mixing together theelectrochemically active material (a), the binder (b), the electricallyconductive agent (c), additional water and/or organic solvent ifnecessary, and optional additives such as those mentioned above, if any.These substances can be mixed together by agitation with a known meanssuch as stirrer, bead mill or high-pressure homogenizer, such as isdemonstrated in the Examples below.

A suitable mixer should be capable of stirring the slurry components tosuch an extent that a satisfactory dispersion is produced andagglomeration of the active material particles is prevented. The degreeof dispersion can be measured with a particle gauge, and mixing anddispersion are usually carried out to ensure that agglomerates of 100nanometers or more are not present. Examples of suitable mixers includeball mills, sand mills, pigment dispersers, grinding machines,ultrasonic dispersers, homogenizers, planetary mixers and Hobart mixers.

The present invention also provides an electrode comprising:

(a) an electrical current collector; and

(b) a cured film formed on the electrical current collector, wherein thefilm is deposited from any of the slurry compositions described above.

The current collector (a) is not particularly limited if it is made of aconductive material. In a lithium ion secondary battery, a currentcollector made of a metal such as iron, copper, aluminum, nickel orstainless steel can be used. Typically, aluminum or copper in sheet,foil, or mesh form is used.

Although the shape and thickness of the current collector are notparticularly limited, the current collector is usually in the form of asheet or foil having a thickness of about 0.001 to 0.5 mm.

Each of the components in the slurry composition used to form the filmdeposited on the electrical current collector may be selected from thecomponents described earlier. The binder (b) may also further compriseany of the crosslinking agents described above.

The electrode can be manufactured by applying the above slurry to thesurface of a suitable current collector to form a coating and curing thecoating by subjecting the coated current collector to conditions for atime sufficient to allow reactive components in the coating to react andform a hardened film.

The method of applying the slurry to the current collector is notparticularly limited. The slurry may for example be applied by doctorblade coating, dip coating, reverse roll coating, direct roll coating,gravure coating, extrusion coating, immersion or brushing. Although theapplication quantity of the slurry is not particularly limited, thethickness of the active material layer formed after the liquid medium isremoved is typically 25 to 150 microns (μm), such as 30 to 125 μm.

The method of curing or crosslinking the coating film after applicationcan for example be done by heating at elevated temperature, such as 50to 150° C., or 50 to 140° C. The time of heating will depend somewhat onthe temperature. Generally, higher temperatures require less time forcuring. Typically, curing times are for at least 10 minutes, such as 15to 60 minutes. The extent of cure or crosslinking is typically measuredas resistance to solvents such as methyl ethyl ketone (MEK). The test isperformed as described in ASTM D-540293, published 1999. The number ofdouble rubs, one back and forth motion, is reported. This test is oftenreferred to as “MEK Resistance”.

The present invention additionally provides an electrical storage devicesuch as a battery, comprising: (a) the electrode described above; (b) acounter electrode; and (c) an electrolyte. The electrolyte (c) typicallycomprises a lithium salt, such as any of those listed above, dissolvedin a solvent. Suitable solvents include organic carbonates such asethylene carbonate, diethyl carbonate and dimethyl carbonate. Electricalstorage devices of the present invention typically demonstrate anelectrical capacity of at least 60 mAh/g, or at least 65 mAh/g, or atleast 70 mAh/g, at 6.4C discharge.

As used herein, unless otherwise expressly specified, all numbers suchas those expressing values, ranges, amounts or percentages may be readas if prefaced by the word “about”, even if the term does not expresslyappear. Also, any numerical range recited herein is intended to includeall sub-ranges subsumed therein. Singular encompasses plural and viceversa. For example, although reference is made herein to “a” reactionproduct, “an” electrically active material, “a” crosslinker, and thelike, one or more of each of these and any other components can be used.As used herein, the term “polymer” refers to oligomers and bothhomopolymers and copolymers, and the prefix “poly” refers to two ormore. The term “resin” is used interchangeably with “polymer”. Includingand like terms means including but not limited to. When ranges aregiven, any endpoints of those ranges and/or numbers within those rangescan be combined within the scope of the present invention.

Each of the characteristics and examples described above, andcombinations thereof, may be said to be encompassed by the presentinvention. The present invention is thus drawn to the followingnonlimiting aspects:

-   -   1. A lithium ion battery electrode slurry composition        comprising:        -   (a) an electrochemically active material capable of lithium            intercalation and deintercalation;        -   (b) a binder dispersed in an aqueous or organic medium and            comprising a reaction product of a reaction mixture            comprising one or more epoxy functional polymer(s) and one            or more acid functional acrylic polymer(s); and        -   (c) an electrically conductive agent.    -   2. The electrode slurry composition according to aspect 1,        further comprising a thickener such as a carboxymethylcellulose.    -   3. The electrode slurry composition according to any of aspects        1 to 2, wherein the mixture of polymers comprises at least 70        percent by weight of one or more epoxy functional polymer(s) and        up to 30 percent by weight of one or more acid functional        acrylic polymer(s), wherein the percentages by weight are based        on the total weight of the reaction product.    -   4. The electrode slurry composition according to any of aspects        1 to 3, wherein the binder (b) further comprises a crosslinking        agent such as an aminoplast, a polycarbodiimide, a polyepoxide        or a mixture or combination of any of the foregoing.    -   5. The electrode slurry composition according to any of aspects        1 to 4, wherein the electrochemically active material (a)        comprises LiCoO₂, LiNiO₂, LiFePO₄, LiCoPO₄, LiMnO₂, LiMn₂O₄,        Li(NiMnCo)O₂, Li(NiCoAl)O₂, carbon-coated LiFePO₄, graphite,        silicon compounds, tin, tin compounds, or a mixture or        combination of any of the foregoing.    -   6. The electrode slurry composition according to any of aspects        1 to 5, wherein the electrically conductive agent (c) comprises        graphite, acetylene black, furnace black, graphene or a mixture        or combination of any of the foregoing.    -   7. The electrode slurry composition according to any of aspects        1 to 6, wherein the binder (b) is dispersed in an aqueous        medium, and wherein the slurry further comprises an organic        solvent.    -   8. The electrode slurry composition according to any of aspects        1 to 7, wherein the slurry is essentially free of        N-Methyl-2-pyrrolidone and/or wherein the binder (b) is        essentially free of a polyvinylidene fluoride polymer.    -   9. The electrode slurry composition according to any of aspects        1 to 8, wherein the electrochemically active material (a) is        present in amounts of 70 to 98 percent by weight; the binder (b)        is present in amounts of 1 to 10 percent by weight and the        electrically conductive agent (c) is present in amounts of 1 to        20 percent by weight, the percentages by weight being based on        the total weight of solids in the slurry.    -   10. An electrode comprising:        -   (a) an electrical current collector; and        -   (b) a cured film formed on the electrical current collector,            wherein the film is deposited from the electrode slurry            composition according to any of aspects 1 to 9.    -   11. The electrode according to aspect 10, wherein the electrical        current collector (a) comprises copper or aluminum in the form        of a mesh, sheet or foil.    -   12. An electrical storage device comprising:        -   (a) the electrode according to any of aspects 10 or 11,        -   (b) a counter electrode, and        -   (c) an electrolyte.    -   13. The electrical storage device according to aspect 12,        wherein the electrolyte (c) comprises a lithium salt dissolved        in a solvent such as an organic carbonate.

EXAMPLES

Illustrating the invention are the following examples that are not to beconstrued as limiting the invention to their details. All parts in theExamples, as well as throughout the specification, are by weight unlessotherwise indicated.

In the following Examples, Examples 1-3 each demonstrate the synthesisof an epoxy-functional acrylate polymer dispersed in an aqueous mediumby chain extension using an acid functional acrylic polymer and anepoxy-functional polymer.

Examples 4-6 each demonstrate the synthesis of an aqueous binder.

Examples 7-9 each demonstrate the preparation of a lithium ion batteryelectrode slurry and the coating of an electrical current collector inaccordance with the present invention.

Example 10 is a comparative example demonstrating the preparation of asolution of PVDF in NMP.

Example 11 is a comparative example demonstrating the preparation of aPVDF slurry and the coating of an electrical current collector with thePVDF slurry.

Example 1

An epoxy-functional acrylic polymer dispersed in an aqueous medium wasprepared as described in the following three stages.

Stage 1—An acid functional acrylic polymer with a theoretical acid valueof 103.6 was prepared as follows:

Ingredients Amount (gram) Charge 1: Butyl ether of ethylene glycol 542.0BUTVAR B-98 - (Polyvinyl Butyral Resin, 101.2 available from ElectronMicroscopy Sciences) Charge 2: Di-tertiary amyl peroxide 13.8 (premixed)Butyl ether of ethylene glycol 53.3 Charge 3: Ethyl acrylate 401.3(premixed) Styrene 13.3 Methacrylic acid 254.1 Charge 4: N-butanol 64.1(premixed) N-Amyl alcohol 154.6

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. By “ambient” is meant without the application ofheat or other energy; for example, when a mixture of monomers undergoesa polymerization reaction without applying heat to prompt the reaction,the reaction is said to occur under ambient conditions. Usually, ambienttemperature ranges from 60 to 90° F. (15.6 to 32.2° C.), such as atypical room temperature, 72° F. (22.2° C.).

The temperature was increased to reflux (˜160° C.), at which time thecatalyst premix of Charge 2 was added over 205 minutes. Five (5) minutesafter the start of Charge 2, Charge 3 was added over 180 minutes. Uponcompletion of Charges 2 and 3, the reaction was held for additional 60minutes at reflux (˜160° C.). Thereafter the reaction temperature wascooled to 80° C. and Charge 4 was added with a subsequent 15-minute holdperiod. The polymeric product thus formed had a theoretical solidscontent of 49.1%.

Stage 2—An epoxy-functional polymer with an epoxy-equivalent weight inthe range of 5500-6500 as measured by titration with 0.1 N perchloricacid according to ASTM D1652 was prepared as follows:

Ingredients Amount (gram) Charge 1: EPON 828 620.0 Bisphenol A 327.0Xylene 76.0 Ethyl triphenyl phosphonium iodide 0.7 Charge 2: Ethyl etherof diethylene glycol 538.0 Charge 3: Monoethanol amine 6.6 (premixed)Ethyl ether of diethylene glycol 5.6

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was then increased to 110° C. andthe reaction mixture was held at this temperature for 30 minutes. Thetemperature was then increased to 160° C. over 30 minutes to avoidexcess exotherm, and set to 170° C. and held at this temperature tillthe epoxy equivalent weight was in the range of 2200-2450, as measuredby titration with 0.1 N perchloric acid according to ASTM D1652. Thenthe reaction mixture was cooled to 125° C. and Charge 2 was added,followed by addition of Charge 3. The mixture was then held for 90minutes. Measured epoxy equivalent weight was in the range of 5500 to6500. The polymeric product thus formed had a theoretical solids contentof 60.6%.

Stage 3—An epoxy-functional acrylic polymer dispersed in an aqueousmedium was prepared from the acid functional acrylic polymer obtainedfrom stage 1 and the epoxy-functional polymer obtained from stage 2 asfollows:

Ingredients Amount (gram) Charge 1: Acid functional acrylic polymer fromStage 1 87.5 Dimethylethanol amine 2.5 Ethyl ether of diethylene glycol7.3 Charge 2: Epoxy functional polymer from Stage 2 400.0 Charge 3:Deionized water 226.5 (premixed)

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was then increased to 90° C. andthen Charge 2 was added slowly so that the temperature did not exceed105° C. The contents of the flask were held at this temperature for 60minutes, followed by cooling to 70° C. Charge 3 was preheated to 70° C.and added over 60 minutes followed by a hold of 30 minutes. Thepolymeric product thus formed had a theoretical solids content of 41.5%.

Example 2

An epoxy-functional acrylic polymer dispersed in an aqueous medium wasprepared as described in the following three stages:

Stage 1—An acid-functional acrylic polymer with a theoretical acid valueof 103.6 was prepared as follows:

Ingredients Amount (gram) Charge 1: Butyl ether of ethylene glycol 542.0Charge 2: Di-tertiary amyl peroxide 13.8 (premixed) Butyl ether ofethylene glycol 53.3 Charge 3: Ethyl acrylate 502.5 (premixed) Styrene13.3 Methacrylic acid 254.1 Charge 4: N-butanol 64.1 (premixed) N-Amylalcohol 154.6

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was increased to reflux (˜160° C.),at which time the catalyst premix of Charge 2 was added over 205minutes. Five (5) minutes after the start of Charge 2, Charge 3 wasadded over 180 minutes. Upon completion of Charges 2 and 3, the reactionwas held for additional 60 minutes at reflux (˜160° C.). Thereafter thereaction temperature was cooled to 80° C. and Charge 4 was added with asubsequent 15-minute hold period. The polymeric product thus formed hada theoretical solids content of 49.1%.

Stage 2—An epoxy-functional polymer with an epoxy-equivalent weight inthe range of 5500-6500 as measured by titration with 0.1 N perchloricacid according to ASTM D1652 was prepared as follows:

Ingredients Amount (gram) Charge 1: EPON 828 620.0 Bisphenol A 327.0Xylene 76.0 Ethyl triphenyl phosphonium iodide 0.7 Charge 2: Ethyl etherof diethylene glycol 538.0 Charge 3: Monoethanol amine 6.6 (premixed)Ethyl ether of diethylene glycol 5.6

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was then increased to 110° C. andthe reaction mixture was held at this temperature for 30 minutes. Thetemperature was then increased to 160° C. over 30 minutes to avoidexcess exotherm, and set to 170° C. and held at this temperature tillthe epoxy equivalent weight was in the range of 2200-2450 as measured bytitration with 0.1 N perchloric acid according to ASTM D1652. Then thereaction mixture was cooled to 125° C. and Charge 2 was added, followedby addition of Charge 3 and the mixture was then held for 90 minutes.Measured epoxy equivalent weight was in the range of 5500 to 6500. Thepolymeric product thus formed had a theoretical solids content of 60.6%.

Stage 3—An epoxy-functional acrylic polymer dispersed in an aqueousmedium was prepared from the acid functional acrylic polymer obtainedfrom stage 1 and the epoxy-functional polymer obtained from stage 2 asfollows:

Ingredients Amount (gram) Charge 1: Acid functional acrylic polymer fromStage 1 87.5 Dimethylethanol amine 3.1 Ethyl ether of diethylene glycol2.5 Charge 2: Epoxy functional polymer from Stage 2 270.0 Charge 3:Dimethyl ethanol amine 4.2 Charge 4: Deionized water 136.0 Charge 5:Epoxy-functional polymer of Stage 2 134.0 Charge 6: Deionized water 32.0

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was then increased to 90° C. andthen Charge 2 was added slowly so that the temperature did not exceed105° C. The contents of the flask were held at this temperature for 60minutes, followed by cooling to 90° C. Charge 3 was added followed bythe addition of Charge 4 over 30 minutes. The reaction solution was heldat 90° C. for 15 minutes, followed by the addition of Charge 5 over 15minutes. After holding the solution for 15 minutes, Charge 6 was added.The polymeric product thus formed had a theoretical solids content of41.5%.

Example 3

An epoxy-functional acrylic polymer dispersed in an aqueous medium wasprepared as described in the following three stages:

Stage 1—An acid-functional acrylic polymer with a theoretical acid valueof 103.6 was prepared as follows:

Ingredients Amount (gram) Charge 1: Butyl ether of ethylene glycol 542.0BUTVAR B-98 - (Polyvinyl Butyral Resin) 101.2 Charge 2: Di-tertiary amylperoxide 13.8 (premixed) Butyl ether of ethylene glycol 53.3 Charge 3:Ethyl acrylate 401.3 (premixed) Styrene 13.3 Methacrylic acid 254.1Charge 4: N-butanol 64.1 (premixed) N-Amyl alcohol 154.6

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was increased to reflux (˜160° C.),at which time the catalyst premix of Charge 2 was added over 205minutes. Five (5) minutes after the start of Charge 2, Charge 3 wasadded over 180 minutes. Upon completion of Charges 2 and 3, the reactionwas held for additional 60 minutes at reflux (˜160° C.). Thereafter thereaction temperature was cooled to 80° C. and Charge 4 was added with asubsequent 15-minute hold period. The polymeric product thus formed hada theoretical solids content of 49.1%.

Stage 2—An epoxy-functional polymer with an epoxy-equivalent weight inthe range of 9000-11000 as measured by titration with 0.1 N perchloricacid according to ASTM D1652 was prepared as follows:

Ingredients Amount (gram) Charge 1: EPON 828 620.0 Bisphenol A 327.0Xylene 76.0 Ethyl triphenyl phosphonium iodide 0.7 Charge 2: Ethyl etherof diethylene glycol 538.0 Charge 3: Monoethanol amine 9.1 (premixed)Ethyl ether of diethylene glycol 5.6

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was then increased to 110° C. andthe reaction mixture was held at this temperature for 30 minutes. Thetemperature was then increased to 160° C. over 30 minutes to avoidexcess exotherm, and set to 170° C. and held at this temperature tillthe epoxy equivalent weight as measured by titration with 0.1 Nperchloric acid according to ASTM D1652 was in the range of 2200-2450.Then the reaction mixture was cooled to 125° C. and Charge 2 was added,followed by addition of Charge 3 and held for 90 minutes. Measured epoxyequivalent weight was in the range of 9000 to 11000. The polymericproduct thus formed had a theoretical solids content of 60.6%.

Stage 3—An epoxy-functional acrylic polymer dispersed in an aqueousmedium was prepared from the acid functional acrylic polymer obtainedfrom stage 1 and the epoxy-functional polymer obtained from stage 2 asfollows:

Ingredients Amount (gram) Charge 1: Acid functional acrylic polymer fromStage 1 87.5 Dimethylethanol amine 3.1 Ethyl ether of diethylene glycol2.5 Charge 2: Epoxy functional polymer from Stage 2 270.0 Charge 3:Dimethyl ethanol amine 4.2 Charge 4: Deionized water 136.0 Charge 5:Epoxy-functional polymer of Stage 2 134.0 Charge 6: Deionized water 32.0

To a suitable reaction vessel equipped with a stirrer, reflux condenser,thermometer, heating mantle and nitrogen inlet, Charge 1 was added atambient temperature. The temperature was then increased to 90° C. andthen Charge 2 was added slowly so that the temperature did not exceed105° C. The contents of the flask were held at this temperature for 60minutes, followed by cooling to 90° C. Charge 3 was added followed bythe addition of Charge 4 over 30 minutes. The reaction solution was heldat 90° C. for 15 minutes, followed by the addition of Charge 5 over 15minutes. After holding the solution for 15 minutes, Charge 6 was added.The polymeric product thus formed had a theoretical solids content of41.5%.

Example 4

To a plastic container was added phenol-formaldehyde resin, HRJ-13078(available from Si Group, 1.3 grams), methylatedbenzoguanamine-formaldehyde resin, MAPRENAL MF 984/80B (available fromIneos Melamines, 0.6 grams), and the epoxy-functional acrylic polymerdispersed in an aqueous medium (112.5 grams) from Stage 3 of Example 1.This blend was then placed in a dual-asymmetric centrifugal mixer andmixed at 2350 rpm for 5 minutes.

Example 5

To a plastic container was added phenol-formaldehyde resin, HRJ-13078(available from Si Group, 1.3 grams), methylatedbenzoguanamine-formaldehyde resin, MAPRENAL MF 984/80B (available fromIneos Melamines, 0.6 grams), and the epoxy-functional acrylic polymerdispersed in an aqueous medium (112.5 grams) from Stage 3 of Example 2.This blend was then placed in a dual-asymmetric centrifugal mixer andmixed at 2350 rpm for 5 minutes.

Example 6

To a plastic container was added phenol-formaldehyde resin, HRJ-13078(available from Si Group, 1.3 grams), methylatedbenzoguanamine-formaldehyde resin, MAPRENAL MF 984/80B (available fromIneos Melamines, 0.6 grams), and the epoxy-functional acrylic polymerdispersed in an aqueous medium (112.5 grams) from Stage 3 of Example 3.This blend was then placed in a dual-asymmetric centrifugal mixer andmixed at 2350 rpm for 5 minutes.

Example 7

To a small plastic mixing cup was added 1.9 grams of ethanol, 19 gramsof deionized water, and 0.2 grams of sodium carboxymethylcellulose.After mixing to achieve a clear solution, 0.7 grams of TIMCAL C-NERGY™Super C65 conductive carbon (available from TIMCAL) was added. Thisblend was placed in a dual-asymmetric centrifugal mixer and mixed at2000 rpm for 5 minutes. Cathode active powder lithium ion phosphate(LFP) (Life Power P2 lot #1110GY195 available from Phostech Lithium,Inc) (7.9 grams) was added to this mixed blend, and the resultingcombination was subjected to a second mixing in a dual asymmetriccentrifugal mixer at 2000 rpm for 5 minutes. Next, 1.5 grams of theaqueous binder from Example 4 was added and the combination wassubjected to a third mixing in a dual-asymmetric centrifugal mixer at2000 rpm for 5 minutes. And finally, 3.6 grams of 2-butoxyethanolsolvent was added and the mixture was mixed in a dual-asymmetriccentrifugal mixer at 2000 rpm for 5 minutes for the final time.

A wet film was prepared on pre-cleaned aluminum foil (foil of aluminumalloy 1085 from Targray pre-cleaned with acetone) by a draw-downapplication of this formulated slurry using an automatic film coater(MSK-AFA-11 from MTI Corporation) using an adjustable doctor blade at arate of 89 mm/sec. This wet film was heated in an oven to a maximumtemperature of 140° C. for at least 10 minutes. After cooling, anaverage dry film thickness of 53 microns was determined from fivemeasurements with a micrometer.

Example 8

To a small plastic cup was added 2.2 grams of ethanol, 22.4 grams ofdeionized water, and 0.2 grams of sodium carboxymethylcellulose. Aftermixing to a clear solution, 0.8 grams of TIMCAL C-NERGY™ Super C65conductive carbon was added. This blend was placed in a dual-asymmetriccentrifugal mixer and mixed at 2000 rpm for 5 minutes. Cathode activepowder lithium ion phosphate (LFP) (Life Power P2 lot #1110GY195available from Phostech Lithium, Inc) (7.9 grams) was added to thismixed blend, and the resulting combination was subjected to a secondmixing in a dual asymmetric centrifugal mixer at 2000 rpm for 5 minutes.Next, 1.5 grams of the aqueous binder from Example 5 was added and thecombination was subjected to a third mixing in a dual-asymmetriccentrifugal mixer at 2000 rpm for 5 minutes. And finally, 3.6 grams of2-butoxyethanol solvent was added and the mixture was mixed in adual-asymmetric centrifugal mixer at 2000 rpm for 5 minutes for thefinal time.

A wet film was prepared on pre-cleaned aluminum foil (foil of aluminumalloy 1085 from Targray pre-cleaned with acetone) by a draw-downapplication of this formulated slurry using an automatic film coater(MSK-AFA-11 from MTI Corporation) using an adjustable doctor blade at arate of 89 mm/sec. This wet film was heated in an oven to a maximumtemperature of 140° C. for at least 10 minutes. After cooling, anaverage dry film thickness of 53 microns was determined from fivemeasurements with a micrometer.

Example 9

To a small plastic mixing cup was added 2.2 grams of ethanol, 22.4 gramsof deionized water, and 0.2 grams of sodium carboxymethylcellulose.After mixing to a clear solution, 0.8 grams of TIMCAL C-NERGY™ Super C65conductive carbon was added. This blend was placed in a dual-asymmetriccentrifugal mixer and mixed at 2000 rpm for 5 minutes. Cathode activepowder lithium ion phosphate (LFP) (Life Power P2 lot #1110GY195available from Phostech Lithium, Inc) (9.1 grams) was added to thismixed blend, and the resulting combination was subjected to a secondmixing in a dual asymmetric centrifugal mixer at 2000 rpm for 5 minutes.Next, 1.6 grams of the aqueous binder from Example 6 was added and thecombination was subjected to a third mixing in a dual-asymmetriccentrifugal mixer at 2000 rpm for 5 minutes. And finally, 4.4 grams of2-butoxyethanol solvent was added and the mixture was mixed in adual-asymmetric centrifugal mixer at 2000 rpm for 5 minutes for thefinal time.

A wet film was prepared on pre-cleaned aluminum foil (foil of aluminumalloy 1085 from Targray pre-cleaned with acetone) by a draw-downapplication of this formulated slurry using an automatic film coater(MSK-AFA-11 from MTI Corporation) using an adjustable doctor blade at arate of 89 mm/sec. This wet film was heated in an oven to a maximumtemperature of 140° C. for at least 10 minutes. After cooling, anaverage dry film thickness of 58 microns was determined from fivemeasurements with a micrometer.

Example 10 (Comparative)

To a plastic container was added solvent grade N-methyl-2-pyrrolidone(available from Ashland, 570.7 grams). While stirring with a Cowlesblade, polyvinylidene difluoride, KYNAR HSV 900 PVDF (available fromArkema, 29.3 grams) was added in portions. Stirring was continued untilthe polymer was completely dissolved.

Example 11 (Comparative)

To a plastic cup was added N-methyl-2-pyrrolidone (15.7 grams), thebinder solution from Example 10 (27.66 grams) and 1.35 grams of TIMCALC-NERGY™ Super C65 conductive carbon. This blend was placed in adual-asymmetric centrifugal mixer and mixed at 2350 rpm for 5 minutes.Cathode active powder lithium ion phosphate (LFP) (Life Power P2 lot#1110GY195 available from Phostech Lithium, Inc) (15.3 grams) was addedto this mixed blend, and the resulting combination was subjected to asecond mixing in a dual-asymmetric centrifugal mixer at 2350 rpm for 5minutes to produce formulated slurry.

A wet film was prepared on pre-cleaned aluminum foil (foil of aluminumalloy 1085 from Targray pre-cleaned with acetone) by a draw-downapplication of this formulated slurry using an automatic film coater(MSK-AFA-11 from MTI Corporation) using an adjustable doctor blade at arate of 89 mm/sec. This wet film was heated in an oven to a maximumtemperature of 120° C. for at least 10 minutes. After cooling, anaverage dry film thickness of 44 microns was determined from fivemeasurements with a micrometer.

The dual-asymmetric centrifugal mixer that was used in the examplesabove was a model DAC 400.1 FVZ from FlackTec, Inc. or model ARM-310Thinky USA, Inc.

The dry coated foils obtained from Examples 7 to 9 and ComparativeExample 11 were studied for their electrochemical performance as batteryelectrode. For this purpose, the dry coated foils were passed through aroll calendar press (MTI Corporation) to achieve 25-30% compression.After vacuum drying, two coin-type half-cell batteries per dry coatedfoil were assembled using lithium metal as the anode and one-molar LiPF6in ethylene carbonate, diethyl carbonate and dimethyl carbonate solventsas the electrolyte. The coin cell batteries were then tested on abattery tester (Arbin Instruments) using a potential window of 4.1-2.5Volts for 5 cycles each at currents corresponding to 0.2C, 0.4C, 0.8C,1.6C, 3.2C and 6.4C charge/discharge rates, followed by 25 cycles at thecurrent corresponding to a 1C rate. Discharge capacity in milliamp-hoursper gram of lithium iron phosphate was calculated from the average ofthe first 5 cycles for each C-rate. Discharge capacity averages from thehigher capacity coin-type half-cell of the two replicate cells for agiven dry coated foil are reported in Table 1. Capacity retention wascalculated from the quotient of the discharge capacity after the firstcharge-discharge cycle at 1C and the last charge-discharge cycle at 1Cand reported as percentage according to the equation: 100×first cyclecapacity/last cycle capacity.

Note that “C-rate” refers to a current value that is required to fullydischarge a cell having a constant electrical capacitance in a timeperiod equal to the inverse of the C-rate values in hours. For example,discharge capacity at 0.2C refers to dry coated film capacity inmillamp-hours per gram of lithium iron phosphate at a current valuerequired to fully discharge the battery in 5 hours. Similarly dischargecapacity at 1C refers to dry coated film capacity in milliamp-hours pergram of lithium iron phosphate at a current value required to fullydischarge the battery in 1 hour.

The performance data measured as set forth above at 25° C. for thecoin-cell batteries prepared from the dry coated aluminum foils obtainedfrom Examples 7 to 9 and Comparative Example 11 are summarized in Table1.

TABLE 1 Discharge data at 25° C. for coin-cell batteries prepared fromExamples. Table 1 shows cell specific capacity (milliamp- hours pergram) for various discharge C-rates (per hour) % Capacity Retentionafter about Discharge C-Rate (hour⁻¹) 25 cycles at Example 0.2 0.4 0.81.6 3.2 6.4 1.0 C-rate of 1.0  7 145 117 72 127 91  8 143 114 69 124 91 9 139 111 71 120 91 11 158 156 151 140 116 66 146 93 (COMPARATIVE)

As shown in table 1, batteries prepared with the slurries of the presentinvention compared to a battery prepared from a conventional NMP-basedslurry (Comparative Example 11) demonstrate: (1) 90% of the controlcapacity for the 5-hour discharge (0.2C rate); (2) capacity equivalentto or better than that of a conventional NMP-based slurry (ComparativeExample 11) for the 0.156 hr discharge (6.4C rate) and (3) equivalentcycle life (capacity retention after 25 cycles at 1C rate).

Example 12

Nonlinear Stabilizer Acrylic 1 was Prepared as Follows:

Ingredients Parts by weight Charge #1 Butyl Acetate 877.6 Charge #2LUPEROX 270¹ 32.2 Butyl Acetate 247.8 Charge #3 Butyl Acrylate 123.9Butyl Methacrylate 247.8 2-Ethylhexyl Acrylate 722.8 Styrene 123.9Glycidyl Methacrylate 826.0 Allyl Methacrylate 20.7 Charge #4 ButylAcetate 41.3 Charge #5 LUPEROX 270 10.7 Butyl Acetate 26.9 Charge #6Butyl Acetate 98.4 ¹LUPEROX270 is t-butyl-per-3,5,5-trimethylhexanoate,available from Arkema, Inc.

Charge #1 was added into a 5-liter, 4-necked flask equipped with amotor-driven steel stir blade, a thermocouple, a nitrogen inlet, and awater-cooled condenser. The reaction mixture was heated to reflux(approximately 125° C.), by a mantle controlled by the thermocouple viaa temperature feedback control device. Charge #2 and #3 were addeddropwise via addition funnels over 3 hours, while the reaction mixturecontinued to reflux. After the addition was complete, the additionfunnel that had contained Charge #3 was rinsed with Charge #4 into thereaction flask, and the reaction mixture was held at reflux for 60minutes. Charge #5 was added over 30 minutes. After the addition wascomplete, the additional funnel that contained Charge #5 was rinsed withCharge #6 into the reaction flask, and the reaction mixture was held atreflux for 1 hour. The acrylic polymer solution thus obtained has atheoretical epoxy equivalent weight of 570 g/equivalent, an approximateMw 33,600 and an approximate Mn 5,400 (measured by gel permeationchromatography using polystyrene standards) with a measured 110° C.solids of 61%.

Example 13

An epoxy functional resin was prepared as follows:

Ingredients Parts by weight Charge #1 Acrylic from Example 12 390.6Solvent Blend A² 250.6 Charge #2 LUPEROX 270 0.40 Solvent Blend A 4.0Charge #3 Ethylene Glycol Dimethacrylate 6.4 Glycidyl Methacrylate 16.0Styrene 25.6 Butyl Acrylate 32.0 Methyl Methacrylate 80.0 Charge #4LUPEROX 270 2.60 Solvent Blend A 48.6 Charge #5 Solvent Blend A 16.0Charge #6 LUPEROX 270 2.0 Solvent Blend A 10.8 Charge #7 Solvent Blend A6.41 ²Solvent Blend A was 49% butyl acetate, and 51% ISOPAR E(isoparaffinic hydrocarbon solvent, available from ExxonMobil ChemicalCompany).

Charge #1 was added into a 2-liter, 4-necked flask equipped with amotor-driven steel stir blade, a thermocouple, a nitrogen inlet, and awater-cooled condenser. The reaction mixture was heated to reflux(approximately 120° C.), by a mantle controlled by the thermocouple viaa temperature feedback control device. Charge #2 and 10.0% by weight ofCharge #3 were added dropwise via addition funnels over 10 minutes, andthen the reaction mixture was held at reflux for 30 minutes. After thehold, Charge #4 and the remainder of Charge #3 were added over 2 hours,while the reaction mixture continued at reflux. After the addition wascomplete, the addition funnel that contained Charge #3 was rinsed withCharge #5 into the reaction flask, and the reaction mixture was held atreflux for 60 minutes. Charge #6 was added over 30 minutes, and then theaddition funnel that had contained Charge #6 was rinsed with Charge #7into the reaction flask. The reaction mixture was held at reflux for 1hour. The reaction product thus obtained had a clear, solution likeappearance and a measured 110° C. solids content of 45%.

Example 14

Stage 1—Polyester Polyol:

Ingredients Parts by weight Charge #1 Glycerin 26.5 Propanediol* 2454.5Methyl Isobutyl Ketone (MIBK) 421.8 Ionol 13.5 Butyl Stannoic Acid 11.2Triisodecyl Phosphite 28.2 Itaconic Acid** 2798.7 Modaflow in 50%MIBK*** 0.36 *available from E.I. Dupont de Nemours. **available fromSupreme Resources ***available from Allnex. Used as a solution (50%) inmethyl isobutyl ketone

Charge #1 was added to a 12 liter 4-necked flask equipped with amotor-driven steel stir blade, a thermocouple, a nitrogen inlet, andDean-Stark trap for azeotropic distillation. The reaction mixture washeated to 190° C., by a mantle controlled by the thermocouple via atemperature feedback control device. The heating continued until theacid value measured less than 15, measured as per ASTM D974 (2014).After the acid value reached <15, reaction heat was set to 120° C. andthe Dean-Stark trap changed to a distillation set up to vacuum distillremaining MIBK. The resulting polyester was stable in 110° C. for amonth. The resulting polymer solution thus obtained has an average Mw1109 and an approximate Mn 593 (measured by gel permeationchromatography using polystyrene standards), 246 hydroxyl value and 110° C./1 hour solids of 94%.

Stage 2—Isocyanate Acrylate:

Ingredients Parts by weight Charge #1 Isophorone Diisocyanate 3362.5Ionol 2.7 Dibutyltin Dilaurate 2.7 Charge #2 2-Hydroxyethyl Acrylate2000

Charge #1 was added to a 12 liter 4-necked flask equipped with amotor-driven steel stir blade, a thermocouple and a water-cooledcondenser. Charge #2 was added dropwise via addition funnel over 4-5hours, maintaining the reaction temperature below 50° C. After theaddition the reaction mixture was held at 50° C. for 1 hour. Theresulting clear solution isocyanate equivalent weight was 410 g/eq.

Stage 3—Polyester-Urethane-Acrylate

Ingredients Parts by weight Charge #1 Stage 2 - Isocyanate Acrylate3689.5 Ionol 3.5 Charge #2 Stage 1 - Polyester Polyol 2150.54 Charge #3n-Butyl Acetate 855.7

Charge #1 was added to a 12 liter 4-necked flask equipped with amotor-driven steel stir blade, a thermocouple and a water-cooledcondenser. Charge #2 was added dropwise via addition funnel over 1 hourwhile maintaining the reaction temperature below 60° C. After theaddition the reaction mixture was held at 80° C. for 30 minutes untilthe isocyanate signal disappeared by Infrared Spectroscopy scanning.After all isocyanate was consumed, Charge #3 was added and cooled toroom temperature. The resulting polymer solution thus obtained had anaverage Mw 1670 and an approximate Mn 1,012 (measured by gel permeationchromatography using polystyrene standards) with a measured 110° C./1hour solids of 85%.

Example 15

A solventborne reaction product of a reaction mixture comprising anepoxy functional polymer and an acid functional acrylic polymer wasprepared as follows:

Solvent 0.2 g Catalyst (methyl dicocoamine) 0.7 g Non aqueous epoxydispersion 80 g of Example 13 Polyester-urethane acrylic 28 g polymer ofExample 14 Oxsol 66 (cut) Anti-gassing 0.2 g agent Melamine (Resimene741) 2 g Catalyst - phenyl acid phosphate 0.6 g Dyna Add F1 Levelingagent 0.1 g RK-5345 Leveling agent 0.2 g (polybutylacrylate)Ethyl,3-ethoxypropionate 35 g

-   -   Oxsol 66 is a proprietary cut of solvents available from        IsleChem on New York, N.Y. 10016    -   Resimene 741: Melamine formaldehyde resin available from INEOS        of Frankfurt Germany D60386    -   Dyna Add F1 is a propretery mix of leveling agents available        from Dynea in Lillestrom, Norway    -   RK-5345 is a polybutyl acrylate in xylene solvent available        from E. I. Dupont de Nemours

All the ingredients were added to a glass beaker in the order listedabove under mild agitation. The entire mixture was stirred an additional10 minutes with no precautions for air entrainment, temperatureregulation or solvent evaporation.

Example 16

A solution was made using M-Pyrol (19.67 grams) and the reaction productof Example 15 (3.58 grams). To a plastic cup was added a portion of thisbinder solution (15.5 grams), conductive carbon Timcal Super C65 (1.0grams), and cathode active powder lithium nickel cobalt manganate(Umicore Cellcore TX/60448, 18 grams). The resulting combination wassubjected to a mixing in a dual-asymmetric centrifugal mixer at 2350 rpmfor 3 minutes to produce a formulated slurry.

A wet film was prepared on pre-cleaned aluminum foil by a draw-downapplication (320-micron gap) of this formulated slurry using a doctorblade. This wet film was heated in an oven to a maximum temperature of140° C. for at 30 minutes. After cooling, an average dry film thicknessof 108 microns was determined from five measurements with a micrometer.

Battery performance data for this coating is shown in following table:

Capacity (mAh/g) 0.1 C 0.2 C 0.5 C 1 C 2 C 164 159 148 138 115

Whereas particular embodiments of this invention have been describedabove for purpose of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

Although various embodiments of the invention have been described interms of “comprising”, embodiments consisting essentially of orconsisting of are also within the scope of the present invention.

What is claimed is:
 1. A lithium ion battery electrode slurrycomposition comprising: (a) an electrochemically active material capableof lithium intercalation and deintercalation; (b) a binder comprising:(i) a crosslinking agent comprising an aminoplast, and (ii) a reactionproduct of a reaction mixture comprising one or more epoxy functionalpolymer(s) and one or more acid functional acrylic polymer(s); and (c)an electrically conductive agent.
 2. The electrode slurry composition ofclaim 1, further comprising a thickener.
 3. The electrode slurrycomposition of claim 1, wherein the binder (b) is dispersed in anaqueous medium.
 4. The electrode slurry composition of claim 3, furthercomprising an organic solvent.
 5. The electrode slurry composition ofclaim 1, wherein the binder (b) is dispersed in an organic medium. 6.The electrode slurry composition of claim 1, wherein the crosslinkingagent further comprises a polycarbodiimide, a polyepoxide, or acombination thereof.
 7. The electrode slurry composition of claim 1,wherein the electrochemically active material (a) comprises LiCoO₂,LiNiO₂, LeFePO₄, LiCoPO₄, LiMnO₂, LiMn₂O₄, Li(NiMnCo)O₂, Li(NiCoAl)O₂,carbon-coated LiFePO₄, graphite, silicon compounds, tin, tin compounds,or a combination thereof.
 8. The electrode slurry composition of claim1, wherein the electrically conductive agent (c) comprises graphite,acetylene black, furnace black, graphene or a mixture or combination ofany of the foregoing.
 9. The electrode slurry composition of claim 1,wherein the slurry is substantially free of N-methyl-2-pyrrolidone. 10.The electrode slurry composition of claim 1, wherein theelectrochemically active material (a) is present in amounts of 70 to 98percent by weight; the binder is present in amounts of 1 to 10 percentby weight; and the electrically conductive agent (c) is present inamounts of 1 to 20 percent by weight, the percentages by weight beingbased on the total weight of solids in the slurry.
 11. The electrodeslurry composition of claim 1, wherein the binder (b) is substantiallyfree of a polyvinylidene fluoride polymer.
 12. The electrode slurrycomposition of claim 1, wherein the binder comprises a reaction mixturecomprising one or more epoxy functional polymers and one or more acidfunctional polymers, wherein the one or more epoxy functional polymersare prepared by reacting together a polyepoxide and (i) a polyaminegroup-containing material and/or (ii) a polyhydroxyl group-containingmaterial.
 13. An electrode comprising: (a) an electrical currentcollector; and (b) a cured film formed on the electrical currentcollector, wherein the film is deposited for a slurry compositioncomprising: (i) an electrochemically active material capable of lithiumintercalation and deintercalation; (ii) a binder dispersed in an aqueousor organic medium and comprising a reaction product of a reactionmixture comprising one or more epoxy functional polymer(s) and one ormore acid functional acrylic polymer(s); and (iii) an electricallyconductive agent.
 14. The electrode of claim 13, wherein the slurrycomposition further comprises a thickener.
 15. The electrode of claim13, wherein the thickener comprises a carboxymethylcellulose.
 16. Theelectrode of claim 13, wherein the electrical current collector (a)comprises copper or aluminum in the form of a mesh, sheet or foil. 17.The electrode of claim 13, wherein the electrically conductive agent(iii) comprises graphite, acetylene black, furnace black, graphene or amixture or combination of any of the foregoing.
 18. An electricalstorage device comprising: (a) the electrode of claim 13, (b) a counterelectrode, and (c) an electrolyte.
 19. The electrical storage device ofclaim 18, wherein the electrolyte (c) comprises a lithium salt dissolvedin a solvent.
 20. The electrical storage device of claim 20, wherein thelithium salt is dissolved in an organic carbonate.